The presence of microscopic organisms in public drinking water is a threat to public health. Two particular pathogenic protozoa pose a significant threat, Giardia Lamblia and Cryptosporidium. Research conducted in 1991 showed the scope of the problem. This research revealed significant presence of these protozoa in the drinking water of several states and Canada. (Rose, J. B., C. P. Gerba and W. Jakubowski. 1991. Survey of Potable Water Supplies for Cryptosporidium and Giardia, Environmental Science and Technology. Vol. 225, no. 8, pp. 1393-1400; LeChevallier, M. W., W. D. Norton and R. G. Lee. 1991. Giardia and Cryptosporidium spp. in Filtered Drinking Water Supplies, Applied and Environmental Microbiology. Vol. 57, no. 9, pp. 2617-2621). In the spring of 1993, the presence of Cryptosporidium in Milwaukee's water supply caused over two dozen deaths. (Gurwitt, Rob. 1994. Something in the Water, Governing. Sept., 1994, pp. 32-38). 400,000 other people suffered from diarrhea, vomiting and intestinal cramps. During 1991 and 1992, 34 waterborne disease outbreaks were reported by the Center for Disease Control. Of these outbreaks, where a cause was found, 64% were associated with Giardia or Cryptosporidium. (Moore et al. 1994. Waterborne Disease in the United States, 1991 and 1992, Journal of the American Water Works Association. February pp. 87-99).
The Surface Water Treatment Rule (SWTR) specifies turbidity regulations for drinking water. The above-noted outbreaks recently caused the Environmental Protection Agency (EPA) to propose amendments to the SWTR. This enhanced rule (ESWTR) will provide additional protection against disease causing pathogens such as Cryptosporidium, Giardia and viruses. (EPA, Jul. 29, 1994. National Primary Drinking Water Regulations: Enhanced Surface Water Treatment Requirements; Proposed Rule, Federal Register, Vol. 59, No. 145). A proposed nation-wide monitoring program called the Information Collection Rule (ICR) will require microbial monitoring over a three year period. These requirements in the ICR are estimated to cost 1,725 water plants $11.8 million. (EPA, Feb. 10, 1994. Monitoring Requirements for Public Drinking Water Supplies; Proposed Rule, Federal Register, Vol. 59, No. 28). Results of the ICR will provide raw data for the determination of the improved regulations in the ESWTR. One regulation scenario projects an estimate of additional capital expenditures for domestic water utilities of $4.5 billion.
The occurrence of an outbreak from microbial pathogens might result from a malfunction of any water treatment system. The prevention of an outbreak could be accomplished through detection of microorganism presence in finished drinking water prior to distribution.
Under the current ICR, slide samples of drinking water are inspected using a microscope by an operator. Using current identification techniques, a microscope operator can process approximately 3-4 samples in a work week. Under EPA regulations, operators are restricted to four working hours at the microscope each work day. This limitation is enforced to prevent operator fatigue and bias in microorganism identification. Even under these limitations, the difficult nature of the required analysis subjects the inspection to human error and subjective bias.
Accordingly, it would be desirable to have an improved system and method for automatically detecting contaminants such as pathogenic protozoa in samples. Such a system and method would make inspection more efficient and accurate.